I also share JayneCobb88’s frustration with the new “save-scumm-proofed” randomised stats, although it’s not so bad that I’ve stopped enjoying the game (after 147 hours play so far). My (admittedly subjective) view is that I’ve also being seeing lots of +1s.
All three stat level-up mechanics tried so far have their pros and cons. The trouble with the original random system, and the new “save-scumm-proofed” one, is that the development of my brothers is chosen partly by me (by the stats I choose) and partly by the RNG; at the moment it feels like my choice has low impact, and the RNG is too dominant.
I’d like to have more control over how my brothers develop, but I still want to agonise over which stats to choose, and have to worry that specialising too much in one stat will mean dangerous weaknesses in others.
A system that might work would be to have fixed upgrades, but instead of being fixed per stat, have it fixed by the order you choose your 3 upgrades: perhaps +4 for the first chosen attribute, +3 for the second and +2 for the third (or maybe +3, +2, +1; or +4, +2, +1…whatever balances). This would allow more specialised builds (but retains the necessary conflict that specialising in one area requires sacrifices in other areas).